The BBC Trust has launched an investigation into BBC Radio 4's religious Thought for the Day slot and the possibility of opening it up to secular and humanist points of view.

The Radio 4 controller, Mark Damazer, said it was a "finely balanced argument" whether non-religious speakers should become a part of the long-running Today programme feature.

Responding to listener complaints on Radio 4's Feedback programme, Damazer said there "may well be quite a strong argument for including secularists and humanists" and said it was "absolutely not a cut and dried issue".

"You should know that the BBC Trust … is currently considering this question and they will come to some kind of conclusion later on this year," said Damazer. "They may well suggest – I have no idea it's for them and not for me – that we should take in a wider range of voices."

Damazer said opening up the slot to other voices would make it lose the distinctiveness it has as a religious feature.

The slot not only gave a voice to a wide range of religions, he said, but also to voices from around the UK rather than "metropolitan figures sitting in a studio in Broadcasting House or the news centre in west London".

"It is I think satisfyingly diverse [but] that does not mean that it should never change its remit or the criteria for selection and I think it is worth looking at. Curiously enough even for people who dislike it, it becomes something of a conversation point quite a lot of the time even when you find yourself being absolutely furious with the speaker's conclusions."

Secular and humanist groups have long campaigned for the slot to be opened up to people outside of religious groups, and in January this year a non-religious version, called Thought for the Afternoon, was broadcast on Radio 4's Saturday afternoon programme, iPM.

One listener told Feedback she found the programme "deeply irritating and quite often quite insulting".

"I would be quite happy with a Thought for the Day with a secular point, some philosophical dilemma, a little bit of science, maybe anything to stop us for a moment and think about something other than the latest drama in the news," she said. "I think it's a very good opportunity to do that, I just feel annoyed it's always the Sikhs or the Muslims or the Jews or the Christians or whatever."

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